The present invention relates to the field of variable size packet demultiplexing and more specifically of concatenated and encapsulated packet demultiplexing.
To achieve reliable data transmission in communication networks, data needs to be encapsulated in data packets. FIG. 1 represents these encapsulations at the different OSI layers (link/MAC) and physical layers (PHY). The data payload represented by the IP protocol data unit (IP-PDU) 1 comprises data coming from the IP layer. Said data is first encapsulated at the MAC layer by adding a MAC header 3 and a MAC trailer 5. Then, the MAC protocol data unit (MAC-PDU) 2, comprising parts 1, 3 and 5, is encapsulated at the physical layer with a physical header 7 and a physical trailer 9. This organization in different sections allows to perform transmission and efficient decapsulation and demultiplexing at destination. FIG. 2 represents the organization of this encapsulation at the MAC layer according to the IEEE 802.3 standard.Three main parts can be defined
a front part called MAC header 3 comprising destination section 11 and source section 13 addresses as well as information section 15 concerning the data carried in the MAC service data unit (MAC-SDU) 1 such as the type of data and the size of the MAC-SDU 1,
the MAC service data unit (MAC-SDU) 1 corresponding to the IP-PDU and therefore to the data to be transmitted,
a MAC trailer 5 indicating the end of the MAC-SDU 1.
In order to improve the efficiency of communication networks, protocol data unit concatenation methods have been developed. These techniques consist in gathering several PDU sections having a common destination in one service data unit. Thus, the required number of headers and trailers is reduced and the performance of the network is optimized. FIG. 3 shows such concatenation of the IP-PDUs 17. The different IP-PDUs are put together in a MAC-SDU 1, encapsulated in a MAC-PDU 2 and sent as a common data unit to their destination. In such cases, demultiplexing of the concatenated IP-PDUs require to determine the beginning and the end of the MAC-SDU 1 comprising said IP-PDUs 17. In the state of the art, this determination is achieved by decoding in the MAC header information concerning the length of the MAC-SDU 1. Such decoding increases the demultiplexing processing load and may therefore reduce the overall throughput of the data transmission.